TANDING outside the Tower Hill Underground station one day last spring, I fell into casual conversation with a woman from Philadelphia. We were part of a group of 12, all waiting for our Original London Walks guide. My new acquaintance had just arrived in town, and was planning to stay nine days, during which she would take two or more guided walks a day. This, it turned out, is what she always does on trips to London. She was wearing sensible shoes.

On our own visits to London, my husband, Tom, and I also go in for Original London Walks, but restrict ourselves to one or two a week. The walking-tour company was founded in the 1960's, and is now operated by David Tucker, an American literary historian, and his wife, Mary, a former actress and trapeze artist; both still lead tours. Its itineraries are wide ranging - among those linked to celebrities, for example, are tours that follow the London footsteps of Oscar Wilde, the Beatles, Charlie Chaplin, Karl Marx and Diana, Princess of Wales. To say nothing of Dickens and Shakespeare. A dozen or more are scheduled on weekdays, while weekends offer a choice of 20.

Both walks and guides are briefly described in a lively little leaflet available in brochure racks in hotels all over town. Many of the 40 or so guides are actors, although there is also at least one former elephant keeper. They are identified by first names, the sole occasional exception - it varies from brochure to brochure - being Edward Petherbridge, known to American audiences as Newman Noggs in the 1981 production of "Nicholas Nickleby" and as Lord Peter Wimsey on television. His wife, Emily Richard, who sometimes leads groups on pub walks, is listed only as "Emily," but is instantly recognizable as Kate Nickleby.

Our guide this morning is named Harry; he is a middle-age man with a trim gray beard and a handsome Roman profile. His beat is the Old Jewish Quarter, a shtetl called Whitechapel. On the way, he will tell us about the history of Jews in the East End, a district much changed by the Blitz, subcontinental immigration and recent gentrification. Harry's grandparents lived in the neighborhood.

We trot through narrow streets, as Harry points out the site of the Great Synagogue (founded about 1720, bombed to extinction 1941); a handsome facade bearing the legend "Soup Kitchen for the Jewish Poor 1902," a charitable work established by the community for the relief of Eastern European immigrants; early 18th-century houses built by Huguenot weavers; the Petticoat Lane street market and Brick Lane, now filled with the spicy scents of dozens of Indian and Bengali restaurants. We pause at a building that was once a church, then a synagogue and is now a mosque.

Throughout our two-hour jaunt, Harry tells stories of the neighborhood and its denizens, from scholars and philanthropists (think Moses Montefiore) to gangsters (the terrifying Kray brothers) and sportsmen (Daniel Mendoza the bare-knuckle fighter, and Abe Saperstein, the inventor of the Harlem Globetrotters). My favorite is his account of the Battle of Cable Street, in which Jews and dockworkers joined forces to deliver a sound drubbing to Oswald Mosley's Blackshirts. The dockworkers may not have liked Jews much, but they really hated Fascists. As for the residents, "Every Jew over 60 claims to have been in it."

The highlight of the tour is the Bevis Marks Synagogue, set in a courtyard off Bevis Marks. (Although it sounds like a department store, the name is actually a corruption of Bury's Marks, after a 12th-century monastic establishment that stood here.) The synagogue dates from a time - it was founded in 1699 and opened in 1701 - when Jews were not allowed to build on a main street, and without Harry to guide us, we might have walked right past it.

IF the synagogue's red brick exterior is largely unremarkable, its interior is both austere and sumptuous. Bevis Marks was founded by Sephardic Jews from Spain and Portugal (a few parts of the service are still in Portuguese). Many of them came through Amsterdam, where they had attended the Portuguese Synagogue, a model, in part, for this one. The references to Dutch church interiors are plain to see; even plainer are the resemblances to the City churches of Sir Christopher Wren, who may or may not have been the architect.

As in Wren churches, the rational, light-filled space appears larger than it is. The carved and gilded tabernacle, with its volutes and Corinthian columns, is pure English Baroque. The seven brass chandeliers, one for each day of the week, would be at home in a Vermeer; the largest was the gift of an Amsterdam congregation. Among the curiosities on display (all of which are in use) is a circumcision chair from 1790. A little gossip with Morris, the shamas (or sexton), tells us that Disraeli's father left the congregation after a quarrel and had his sons baptized as Christians, but not before the infant Benjamin was circumcised here.

As we part company with Harry, I hear a woman asking him for directions to the Whitechapel Bell Foundry, which, although nearby, belongs to another walk. It is easy to combine walks by theme or geography - we could, for example, augment the shtetl walk we have just taken with The Unknown East End or Jack the Ripper Haunts, and some day we shall.

We'll be careful about the Ripper tour, however, since there are imitations, some of them large, noisy groups that have annoyed the newly gentrified to the point where they have lobbed eggs at them. And we'll look for one guided by Donald, who is Donald Rumbelow, the author of "The Complete Jack the Ripper" and a former curator of the notoriously grisly City of London Police Black Museum (a crime museum open by appointment only), credentials that are scary in themselves.

Pub walks are a category of their own. There are two or three every evening, with such names as The Undiscovered London Pub Walk, and Ghosts, Gaslight and Guinness. A highly informal poll (i.e., I chatted with some fellow walkers) indicates that many people's first London Walk was the Along the Thames Pub Walk, a stroll along the south side of the river, past the new Globe Theater, that culminates with a stop at the last galleried coaching inn in London, its courtyard a blaze of light.

It was our own first, and we treasure the memory of our guide, Shaughan, an actor and singer, giving us a rousing version of "John Barleycorn." An unscripted bonus was an encounter with the proprietor of the last armorer's bench in London, who, somewhat under the weather, invited us in to try on amazingly heavy helmets of several historic periods.

Our last walk of this trip answers the question "What if we get lost?" A largish group - there are about 30 of us - has gathered outside the Embankment Underground station in anticipation of Ghosts of the West End. Our leader, Peter, is a tall, theatrical presence with a dashing manner and an even more dashing hat, presumably easy to spot in a crowd.

We set off down Buckingham Street and are introduced to our first ghost - that of Samuel Pepys, no less. He lived at No. 12, and has appeared near the foot of the stairs, graciously greeting guests, most recently in 1957. The apparition of a frolicsome young woman is at home next door, at No. 14.

As we cross The Strand, heading for the Adelphi Theater, a red light cuts Tom and me off from the group. It is just short of 8 p.m. and, having finally crossed the street, we are caught up in the swarm of theatergoers heading into the Adelphi, where "Chicago" is playing. There is no sign of our group in the lobby, there is no sign of our group on the street in any direction. The whole lot of them have, spookily, apparently vanished into thin air. (We later discover that they have ventured into Bull Inn Court, a hidden passageway invisible in the pedestrian throng.)

Oh, rats. Chagrined and annoyed, we walk back to our hotel and call the Original London Walks office to report our problem. Oh, dear, says the nice woman on the other end of the line, you should have phoned right away, and we'd have called Peter on his cellphone and he could have found you. Yeah, well .

Twenty minutes later, the desk calls our room. David Tucker, the president of the company, has come in person to refund our money. Service doesn't get much better than that.

The Original London Walks, Post Office Box 1708, London NW6 4LW, telephone (44-20) 7624-3978 or, for recorded information, (44-20) 7624-9255, www.walks.com, are informally organized. Each takes about two hours and begins and ends at an Underground station. No reservations are necessary; show up at the meeting place, give the guide the equivalent of $8 (about $6.50 for seniors and students), and you're off.

SARAH FERRELL is associate editor of The Sophisticated Traveler of The New York Times Magazine.